Image processing method, image processing apparatus, and programs thereof

ABSTRACT

A color reproduction region of an image formation apparatus is to be effectively used and characteristic in lightness, hue and chroma is to be smoothed. In case of creating tables for separating color into color of coloring agent available in the image formation apparatus, a maximum line in the color reproduction region of the image formation apparatus is defined, internal lines in the color reproduction region of the image formation apparatus are defined and the tables are created by performing interpolation processing on the basis of the maximum line and the internal lines.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to creation of a table used forseparating color into color of coloring agent available in an imageformation apparatus.

[0003] 2. Related Background Art

[0004] Conventionally, processing for separating the color into data ofthe coloring agent available in a color printer (hereinafter, called inkcolor separation processing) is constituted as shown in FIG. 22.Hereinafter, an explanation of the ink color separation processing willbe given with reference to FIG. 22.

[0005] Numeral 2201 denotes a luminance/density conversion unit, numeral2202 denotes a UCR/BG processing unit, numeral 2203 denotes a BGquantity setting unit and numeral 2204 denotes a UCR (under-colorremoval) quantity setting unit. In the luminance/density conversion unit2201, luminance information of 8-bit data of R′, G′ and B′ being inputare respectively converted into C, M and Y data based on followingexpressions.

C=−αlog(R′/255)  (1)

M=−αlog(G′/255)  (2)

Y=−αlog(B′/255)  (3)

[0006] where, α denotes an arbitrary real number.

[0007] Next, the C, M and Y data are respectively converted by use ofβ(Min(C, M, Y),μ) set in a BG coefficient setting unit 1603 and a valueμ% set in a UCR coefficient setting unit 1604 as follows.

C′=C−(μ/100)×Min(C, M, Y)  (4)

M′=M−(μ/100)×Min(C, M, Y)  (5)

Y′=Y−(μ/100)×Min(C, M, Y)  (6)

K′=β(Min(C, M, Y), μ)×(μ/100) ×Min(C, M, Y)  (7)

[0008] where, the β(Min(C, M, Y), μ) denotes a real number which isvaried by the Min(C, M, Y) and the value μ. A dyeing method of K ink canbe set according to a value of this real number.

[0009] Since the UCR quantity and the BG quantity give great influenceto a color reproduction region of the color printer and graininessappeared in printing performed by the printer accompanied by the dyeingmethod of K ink, those quantities become important parameters for thecolor printer.

[0010] However, conventionally, since the UCR quantity is calculated bymultiplying an UCR coefficient μ by the Min(C, M, Y), and the BGquantity is calculated by multiplying the BG coefficient β by the UCRcoefficient μ by the Min(C, M, Y), it was impossible to set optimizedUCR quantity and BG quantity every hue, whereby the following problemsexisted.

[0011] In a certain hue of a target printer, in spite of a fact thatcolor of higher chroma can be outputted, the ink color separationprocessing which can reproduce such the color can not be provided.

[0012] In spite of a fact that influence of graininess caused by the Kink can be more reduced according to combination of ink quantity, thecorresponded ink color separation processing can not be provided.

[0013] In the above conventional example, non-linear characteristic incase of the mixture of plural inks can not be sufficiently absorbed, anddistorted characteristic is remained in lightness, hue and chroma.

SUMMARY OF THE INVENTION

[0014] An object of the present invention is to solve the aboveproblems.

[0015] An object of the first invention is to effectively use a colorreproduction region of an image formation apparatus and avoid to havedistorted characteristic in lightness, hue and chroma.

[0016] An object of the second invention is to reduce the influence ofgraininess caused by K ink.

[0017] The first invention relates to an image processing method, whichcreates a table for separating color into color of coloring agentavailable in an image formation apparatus, is characterized in that amaximum line in the color reproduction region of the image formationapparatus is defined, internal lines in the color reproduction region ofthe image formation apparatus are defined, and interpolation processingis executed on the basis of the maximum line and the internal lines,whereby the table is created.

[0018] The second invention relates to an image processing method, whichcreates a table for separating color into color of coloring agentavailable in an image formation apparatus, is characterized in that afirst line from black to white is defined, plural second lines fromwhite to primary color and secondary color are defined, plural thirdlines from the primary color and the secondary color to black aredefined, and the table is created according to the first line, thesecond lines and the third lines.

[0019] Other objects and features of the present invention will becomeapparent from the following detailed description and the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a block diagram indicating the structure of a firstembodiment;

[0021]FIGS. 2A, 2B and 2C are views for respectively explaining a tableof an ink color separation table unit 105 shown in FIG. 1, a dividingmethod of dividing an input cube into six tetrahedrons and K ink dyeingpoints;

[0022]FIG. 3 is a flow chart indicating the basic structure of an inkcolor separation table creation unit 104 shown in FIG. 1;

[0023]FIGS. 4A, 4B, 4C, 4D, 4E and 4F are views for explaining thedivided six tetrahedrons;

[0024]FIG. 5 is a flow chart for detailedly explaining internalinterpolation processing executed in a step S3-4 shown in FIG. 3;

[0025]FIG. 6 is a view indicating ink contour lines of an internalinterpolation result in a case where changing curves of ink quantity onthree sides of a triangle are exemplified;

[0026]FIG. 7 is a flow chart for explaining two-dimensionalinterpolation processing executed for a target triangle in a step S5-3shown in FIG. 5;

[0027]FIG. 8 is a flow chart for explaining processing executed in astep S7-4, where the ink contour line is created by connecting inkquantity same-level points on total six lines consisted of three sidesof the target triangle and three lines of three maximum value points;

[0028]FIG. 9 is a view for explaining creation of the contour line ofthe target triangle in a case where ink quantity maximum values on threesides are identical each other;

[0029]FIG. 10 is a view for explaining creation of the contour line ofthe target triangle in a case where the maximum values on two sides areidentical each other and the maximum value on one side is equal to zero;

[0030]FIG. 11 is a view for explaining creation of the contour line ofthe target triangle in a case where the maximum values on two sides areidentical each other and points of the maximum values exist on onevertex;

[0031]FIG. 12 is a view for explaining an example of interpolationprocessing executed inside a triangle formed by connecting vertexesW-C-Bk shown in FIG. 2, and indicating examples of the C, M, Y and K inkquantity curves on each side;

[0032]FIGS. 13A, 13B, 13C and 13D are views showing the contour lines ofeach ink in the target triangle shown in FIG. 12;

[0033]FIG. 14 is a view showing the structure of a system according tothe present embodiment;

[0034]FIG. 15 is a flow chart for explaining two-dimensionalinterpolation processing executed in a second embodiment;

[0035]FIG. 16 is a view indicating ink contour lines according to aninternal interpolation processing result in the second embodiment;

[0036]FIG. 17 is a view for explaining the concrete contents of anon-linear approximation step;

[0037]FIG. 18 is a view for explaining an approximation curve when avalue of an approximation parameter a is varied in a step S9-1, wherethe approximation parameter a is set;

[0038]FIG. 19 is a view for explaining creation of the contour line ofthe target triangle in a case where the maximum values on two sides areidentical each other and points of the maximum values exist on onevertex;

[0039]FIGS. 20A, 20B, 20C and 20D are views for explaining the contourlines of each ink in the target triangle;

[0040]FIG. 21 is a view for explaining a method of dividing an inputcube into eight tetrahedrons in a case where color ink of red or greenother than C, M, Y and K is used; and

[0041]FIG. 22 is a view for explaining processing for separating colordata into color of coloring agent available in a conventional colorprinter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] (First Embodiment)

[0043]FIG. 1 is a view showing an outline of image processing accordingto the present embodiment.

[0044] Numeral 101 denotes a color matching processing unit for matchingreproduction characteristic of R, G and B data with color available in aprinter. Numeral 102 denotes an ink color separation processing unit forrespectively converting R′, G′ and B′ multi-level data from the colormatching processing unit 101 into color of coloring agent C′ (cyan), M′(magenta), Y′ (yellow) and K′ (black) available in the printer. Numeral103 denotes a halftone processing unit for respectively converting C′,M′, Y′ and K′ multi-level data from the ink color separation processingunit 102 into data of gradation number which can be expressed by theprinter. Numeral 105 denotes an ink color separation table unit forproviding a table (LUT:look-up table) used in executing interpolationprocessing in the ink color separation processing unit 102. Numeral 104denotes an ink color separation table creation unit for creating the LUTof the ink color separation table unit 105.

[0045]FIG. 14 is a view showing the structure of a system according tothe present embodiment.

[0046] Numeral 1401 denotes a computer, in which patch data used forchecking printer characteristic is held and software used fordetermining a parameter by a UI (user interface) or the like isinstalled. Numeral 1402 denotes a monitor which is connected to thecomputer 1401. Numeral 1402-1 denotes an ink dyeing UI used fordetermining an ink dyeing point. On a displaying portion 1402-2, patchpatterns used for checking the printer characteristic are displayed.Numeral 1403 denotes a color printer for printing predetermined patchdata. Numeral 1405 denotes a patch sample printed by the color printer1403. Numeral 1404 denotes a colorimeter for measuring the patch sample1405.

[0047] Patch data of C′, M′, Y′ and K′ held in the computer 1401 shownin FIG. 14 are respectively transmitted to the printer 1403 through acable, a network (not shown) or the like in order to print the patchdata by the printer 1403. In the printer 1403, the data of C′, M′, Y′and K′ are directly transmitted to the halftone processing unit 103respectively while bypassing the color matching processing unit 101 andthe ink color separation processing unit 102 shown in FIG. 1. In thehalftone processing unit 103, only halftone processing is executed tothe data of C′, M′, Y′ and K′ to perform the print. The printed patchsample 1405 is measured in the colorimeter 1404 shown in FIG. 14 to betaken into the computer 1401. As the patch sample 1405, it may be theone, by which ink characteristic of the printer can be checked, such asgradation patterns of primary colors C, M, Y and K, secondary colors CM,MY, YC, CK, MK and YK, tertiary colors CMY, CMK, MYK and YCK, quarticcolors CMYK or the like available in the printer. In an example shown inFIG. 14, as a printer characteristic input unit 106 shown in FIG. 1, thecolorimeter 1404 is used, and as the ink color separation table creationunit 104, the computer 1401 is used. Therefore, actual processing in theink color separation table creation unit 104 explained in detail withreference to FIG. 2 and the following drawings is executed using thecomputer 1401, and ink color separation tables are created. The createdink color separation tables are downloaded to the ink color separationtable unit 105 in the printer 1403 through a cable or a network (notshown) in order to perform the print from the computer 1401.

[0048] Next, processing of color image data using downloaded data of theink color separation tables will be explained. Color matching processingis executed to multi-level color image data of R, G and B in the colormatching processing unit 101 shown in FIG. 1 so as to match with colorreproduction characteristic of the monitor 1402 being used by a user.The matching processed color image data of R′, G′ and B′ arerespectively separated into data of ink colors in the ink colorseparation processing unit 102 according to the interpolation processingon the basis of data of the previously created ink color separationtable unit 105. The multi-level data of C′, M′, Y′ and K′ separated intothe data of ink colors are respectively converted into data of whichgradation number can be reproduced by the printer in the halftoneprocessing unit 103, then the print is performed in the printer 1403.

[0049] Hereinafter, generation method of data downloaded to the inkcolor separation table unit 105 will be explained in detail withreference to FIGS. 2A to 2C and the following drawings.

[0050]FIG. 2A is a view for explaining the ink color separation tableunit 105. As shown in FIG. 2A, data corresponding to grid pointsdistributed in grid-like on a cube on a RGB three dimensional space isstored as a table corresponding to the input color image data of R′, G′and B′. In the ink color separation processing unit 102, in case of notexisting the input color image data of R′, G′ and B′ on the grid pointsof the ink color separation table unit 105, the interpolation processingis executed using data of adjacent grid points. As interpolation method,although there are plural methods such as a tetrahedron interpolation, acubic interpolation and the like, any interpolation method may be usedbecause ink separation table creation method and image processing of thepresent embodiment are not depended on a specific interpolation method.

[0051]FIG. 2B is a view for explaining concrete table creation methodsrelated to FIG. 3 and the following drawings. Eight vertexes on the cubeshown in FIG. 2A are assumed as W, C, M, Y, R, G, B and Bk, and linesobtained by connecting the above vertexes such as W-C, W-M, W-Y, W-R,W-G and B-Bk are indicated by actual lines or dot lines. When it isassumed that bit number of input data of the ink color separationprocessing unit 102 is eight, coordinates of each of the vertexes W, C,M, Y, R, G, B and Bk are expressed as follows. That is, W=(255, 255,255), which indicates White, i.e., color of printing papers. C=(0, 255,255), which indicates cyan original color. M=(255, 0, 255 ), whichindicates magenta original color. Y=(255, 255, 0), which indicatesyellow original color. R=(255, 0, 0), which indicates red originalcolor. G =(0, 255, 0), which indicates green original color. B =(0, 0,255), which indicates blue original color. Bk =(0, 0, 0), whichindicates black, i.e., the most dark point expressed in the printer.

[0052] The ink color separation table creation method according to thepresent embodiment creates ink color separation tables related to thelines obtained by connecting the above vertexes such as W-C, W-M, W-Y,W-R, W-G, B-Bk and W-Bk. Then, with respect to ink colors correspondingto internal grid points, data of all the tables is created by internalinterpolation processing.

[0053]FIG. 2C is a view for explaining ink (K ink) dyeing points andexplaining a fact that the ink dyeing points can be three-dimensionallyand sequentially controlled by seven dots on the seven lines W-Bk, W-C,W-M, W-Y, W-R, W-G and B-Bk.

[0054]FIG. 3 is a flow chart for explaining functions of the ink colorseparation table creation unit 104.

[0055] A step S3-0, which is a start step, starts to create tables to bedownloaded to the ink color separation table unit 105.

[0056] A step S3-1 is a setting step of setting an ink (k ink) dyeingpoint W0 on the line W-Bk. The ink (k ink) dyeing point on a gray linechanging from white to black is determined using the ink dyeing UI1402-1 shown in FIG. 14 considering characteristic of the printer 1403.A step S3-2, which is a creation step of creating the ink colorseparation table of the line W-Bk, creates the ink color separationtable of the gray line changing from white to black based on the settingstep S3-1 of setting the ink (k ink) dyeing point W0 on the line W-Bk.

[0057] A step S3-3, which is a creation step of creating the ink colorseparation tables of lines W-C, W-M, W-Y, W-R, W-G, and W-B, creates theink color separation tables of the lines White-Cyan, W-magenta,W-Yellow, W-Red, W-Green and W-Blue. A step S3-4, which is a settingstep of setting ink (k ink) dyeing points C0, M0, Y0, R0, G0, and B0 onlines C-Bk, M-Bk, Y-Bk, R-Bk, G-Bk and B-Bk, performs setting of ink (kink) dyeing start points on the lines Cyan-Black, Magenta-Black,Yellow-Black, Red-Black, Green-Black and Blue-Black using the ink dyeingUI 1402-1 shown in FIG. 14. A step S3-5, which is a creation step ofcreating the ink color separation tables of the lines C-Bk, M-Bk, Y-Bk,R-Bk, G-Bk and B-Bk, creates the ink color separation tables of thelines Cyan-Black, Magenta-Black, Yellow-Black, Red-Black, Green-Blackand Blue-Black.

[0058] A step S3-6, which is a step of executing the internalinterpolation processing, creates the ink color separation tablescorresponding to each of grid points inside a space defined by the linesformed in the steps S3-1 to S3-5.

[0059] Tables, in which influence of graininess caused by black ink canbe possibly suppressed while maximizing a color reproduction region inthe printer, can be set by creating tables of setting optimum UCR(under-color removal) quantity or BG quantity every hue in processing ofthe table creation executed in the step S3-5.

[0060] The contents of the internal interpolation processing executed inthe step S3-6 will be explained with reference to FIGS. 4A to 4F and thefollowing drawings. In the internal interpolation processing executed inthe step S3-6, there obtained six divided tetrahedrons of which each ofplanes is formed by a triangle as shown in FIGS. 4A to 4F, and theinterpolation processing is executed every tetrahedron. FIG. 4Aindicates a tetrahedron structured by vertexes W, R, M and Bk. FIG. 4Bindicates a tetrahedron structured by vertexes W, M, B and Bk. FIG. 4Cindicates a tetrahedron structured by vertexes W, C, B and Bk. FIG. 4Dindicates a tetrahedron structured by vertexes W, Y, R and Bk. FIG. 4Eindicates a tetrahedron structured by vertexes W, Y. G and Bk. FIG. 4Findicates a tetrahedron structured by vertexes W, C, G, and Bk.

[0061]FIG. 5 is a flow chart for explaining concrete processing of theinternal interpolation processing executed in the step S3-6.

[0062] A step S5-1, which is a ink color selection step, sequentiallyselects ink colors of cyan, magenta, yellow and black so as to determineink quantity corresponding to each of grids in the following steps. Astep S5-2, which is a step of selecting the tetrahedron and dividing(separating) it into plural triangles, sequentially selects the sixtetrahedrons shown in FIGS. 4A to 4F, and separates those tetrahedronsinto plural triangles. As separating method of separating thetetrahedron into plural triangles, e.g., in a case shown in FIG. 4A, atfirst, the tetrahedron is separated into four triangles of a triangleWMR, a triangle WMBk, a triangle WRBk and a triangle MRBk whichstructure the tetrahedron. Then, internal of the tetrahedron WMRBk isseparated into plural triangles by planes parallel to a triangle WRMcorresponding to the number of grids.

[0063] A step S5-3 is a step of executing two-dimensional interpolationprocessing to target triangles. The contents of the two-dimensionalinterpolation processing executed to each of the triangles will beexplained in detail with reference to FIG. 6 and the following drawings.

[0064] A step S5-4, which is a calculation step of calculating distancebetween an ink contour line of interpolation result and each grid,calculates distance between each of contour lines shown in FIG. 6created according to the step S5-3 of executing the two-dimensionalinterpolation processing and each of grids corresponding to tables inthe ink color separation table unit 105 for each of the triangles. Astep S5-5, which is a step of determining ink quantity of a target grid,determines the shortest distance calculated according to a resultobtained in the step S5-4 which calculates the distance between the inkcontour line of the interpolation result and the each grid as the inkquantity of the target grid.

[0065] A step S5-6 is a step of judging whether or not an undecided gridexists. In a case where the undecided grid exists, the flow returns tothe step S5-4, then processing related to the steps S5-4 and S5-5 areexecuted to a next grid. In the triangle which is targeted in the stepS5-3, when the ink quantity is determined for all the grids, the flowadvances to a step S5-7. The step S5-7, which is a step of judgingwhether or not an unprocessed triangle exists, judges whether or notprocessing is terminated for the plural triangles separated in the stepS5-2. In a case where the unprocessed triangle exists, the flow returnsto the step S5-3, then processing from the step S5-3 to the step S5-6are repeated. In a case where processing is terminated for all thetriangles of the tetrahedron selected in the step S5-2, the flowadvances to a step S5-8. The step S5-8 is a step of judging whether ornot an unprocessed tetrahedron exists. In a case where the unprocessedtetrahedron exists, the flow returns to the step S5-2, then processingfrom the step S5-2 to the step S5-7 are repeated. In a case whereprocessing is terminated for all the tetrahedrons, the flow advances toa step S5-9. The step S5-9 is a step of judging whether or notunprocessed ink color exists. In a case where the unprocessed ink colorexists, the flow returns to the step S5-1, then processing from the stepS5-1 to the step S5-8 are repeated. In a case where processing isterminated for all the ink colors, the flow advances to a portion 3-2.

[0066] Next, concrete processing contents in the step S5-3 of executingthe two-dimensional interpolation processing to the target triangle willbe explained with reference to FIG. 6 and the following drawings.

[0067]FIG. 6 is a view indicating ink contour lines of the internalinterpolation result in a case where ink quantity on three sides of acertain triangle are indicated by curves as shown in FIG. 6. In FIG. 6,change of the ink quantity on a side OA is indicated by a graph which ison the right of the side OA, and a peak of the ink quantity reaches 90%.The change of the ink quantity on a side OB is indicated by a graphwhich is on the left upper of the side OB, and a peak of the inkquantity reaches 30%. The change of the ink quantity on a side AB isindicated by a graph which is under the side AB, and a peak of the inkquantity reaches 60%.

[0068]FIGS. 7 and 8 are flow charts for detailedly explaining thetwo-dimensional interpolation processing executed to the targettriangle. Hereinafter, explanations related to FIGS. 7 and 8 aredescribed with reference to a case in FIG. 6 as an example.

[0069] In FIG. 7, a step S7-1 is a step of detecting the maximum valuepoints of the ink quantity on three sides of the target triangle. A stepS7-2 is a step of obtaining magnitude relationship among three maximumvalues of the three sides. A step S7-3, which is an interpolation stepamong the maximum value points on the three sides, performs aninterpolation operation from values of both ends among the points byconnecting the points of the three maximum values on the three sides bystraight lines. A step S7-4 is a step of creating an ink contour line byconnecting ink quantity same-level points on total six lines consistedof the three sides of the target triangle and three straight linescreated according to the three maximum value points.

[0070] Next, a detailed explanation related to the step S7-4 will begiven with reference to FIG. 8. In a step, S8-1, among the three maximumvalue points, it is defined that the maximum value point is set as apoint D and its magnitude is set as d, the intermediate value point isset as a point H and its magnitude is set as h, and the minimum valuepoint is set as a point J and its magnitude is set as j based on resultsobtained in the steps S7-1 and S7-2. In an example shown in FIG. 6,d=90, h=60 and j=30. A step S8-2 is a step of setting that a vertexobtained by a side including the point D and a side including the pointH is set as A, a vertex obtained by the side including the point H and aside including the point J is set as B, and a vertex obtained by theside including the point J and the side including the point D is set asO. A step S8-3 is a step of setting an interval s and an initial valuei=d−s of contour lines to be created.

[0071] Hereinafter, in a loop from a step S8-4 to a step S8-12, thecontour lines are sequentially created until the ink quantity reaches 0.The step S8-4 is a step of judging whether or not relationship among d,i and h is expressed by an expression of d>i≧h. If Yes in the step S8-4,points of the value i between a straight line DA and a straight line DH,between the straight line DH and a straight line DJ and between thestraight line DJ and a straight line DO are respectively connected inthe step S8-6. In the example shown in FIG. 6, since the interval sbetween the contour lines is expressed by s=15, a contour line for theinitial value i=75 is created as a line G0-G1-G2-G3, and a contour linefor the initial value i=60 is created as a line H0-H-H1-H2. If No in thestep S8-4, the flow advances to the step SB-5. The step S8-5 is a stepof judging whether or not relationship among h, i and j is expressed byan expression of h>i≧j. If Yes in the step S8-5, points of the value ibetween a straight line DA and a straight line AH, between a straightline HB and a straight line HJ, between the straight line HJ and astraight line DJ and between the straight line DJ and a straight line DOare respectively connected in the step S8-7. In the example shown inFIG. 6, contour lines for the initial value i=45 are created as a lineI0-I1 and a line I2-I3-I4-I5, and contour lines for the initial valuei=30 are created as a line J0-J1 and a line J2-J-J3. If No in the stepS8-5, the flow advances to the step S8-8. The step S8-8 is a step ofrespectively connecting points of the value i between the straight lineDA and the straight line AH, between the straight line HB and a straightline BJ and between the straight line JD and the straight line DO. Inthe example shown in FIG. 6, contour lines for the initial values i=15are created as a line K0-K1, a line K2-K3 and a line K4-K5. The stepS8-9 is a step of judging whether or not the initial value i isexpressed by an expression of i=0. If Yes in the step S8-9, creation ofthe contour lines for all the target triangles is terminated, and theflow advances to a portion 7-2. If No in the step S8-9, the flowadvances to the step S8-10. In the step S8-10, an operation of i=i−s isperformed. In the step S8-11, it is judged whether or not i>0. If Yes inthe step S8-11, the flow returns to the step S8-4. If No in the stepS8-11, an operation of i=0 is performed in the step S8-12, and the flowreturns to the step S8-4. As explained above, loop processing from thestep S8-4 to the step S8-12 are repeated until a contour line value issettled into a state of i=0. In FIG. 6, an example of setting theinterval s as s=15 is indicated in order to simplify the explanation.However, in order to make a more precise grid value, it is needless tosay that the contour line should be created every one step by setting sas s=1.

[0072] Hereinafter, with respect to a case that ink curves of threesides are different from those shown in FIG. 6, its operations will beexplained regarding examples shown in FIGS. 9, 10 and 11.

[0073]FIG. 9 shows an example of a case that the ink quantity maximumvalues on the three sides are identical each other. In this case,although it is not specified in FIG. 8, only the step S8-8 being thestep of creating the contour lines is executed, and contour lines asshown in FIG. 9 are created. FIG. 10 shows a case that the ink quantityon one side is equal to zero and the maximum values on other two sidesare identical each other. In this case, points of the value i betweenthe straight line DA and the straight line AH and between the straightline HB and the straight line DO are respectively connected, and contourlines as shown in FIG. 10 are created. FIG. 11 shows a case that themaximum values on the two sides are identical each other and points ofthese maximum values exist on a point A. In this case, since points D, Aand H are the same point, contour line creating processing is notexecuted in the step S8-6 shown in FIG. 8. In the step S8-7, the contourline does not exist because the points D, A and H are the same pointbetween the straight line DA and the straight line AH, the contour linecreating processing is not executed because the points D and H are thesame point between the straight line HJ and the straight line DJ, andprocessing of respectively connecting the points of the value i isexecuted only between the straight line HB and the straight line HJ andbetween the straight line DJ and the straight line DO. In the step S8-8,the contour line does not exist because the points D, A and H are thesame point between the straight line DA and the straight line AH, andprocessing of respectively connecting the points of the value i isexecuted only between the straight line BJ and a straight line JO andbetween the straight line JO and the straight line DO, then contourlines as shown in FIG. 11 are created.

[0074]FIG. 12 is a view for explaining an example of interpolationprocessing executed inside a triangle formed by vertexes W-C-Bk shown inFIG. 2, and indicating examples of curves related to ink color tables ofthe C, M, Y and K colors on each of sides. FIGS. 13A to 13D show thecontour lines every ink color in FIG. 12. FIG. 13A indicates the contourlines of C ink and this case corresponds to a case in FIG. 11. FIG. 13Bindicates the contour lines of M ink and this case corresponds to a casein FIG. 10. FIG. 13C indicates the contour lines of Y ink and this casealso corresponds to the case in FIG. 10. FIG. 13D indicates the contourlines of K ink and this case corresponds to the case in FIG. 10,however, since the K ink is injected from halfway, a region of which inkquantity is zero widely exists and the contour lines of the K ink arecreated from halfway.

[0075] In this manner, in the present embodiment, the internalinterpolation processing is correspondingly executed every ink color onthe basis of ink quantity curves on three sides of a triangle, then theoptimum and independent ink contour lines are created from the inkquantity curves on the three sides. Therefore, by controlling the ink (kink) dyeing points on a gray axis and six hues, i.e., seven ink (k ink)dyeing points on tables of seven lines W-Bk, C-Bk, M-Bk, Y-Bk, R-Bk,G-Bk and B-Bk, the tables of the ink color separation table unit 105 canbe controlled in an input color space in a manner that the ink (k ink)dyeing points can be three dimensionally and sequentially controlled bytotal six planes of a triangle WO-RO-MO, a triangle WO-MO-BO, a triangleWO-BO-CO, a triangle WO-CO-GO, a triangle WO-GO-YO and a triangleWO-YO-RO. Accordingly, the tables, in which the optimum UCR quantity orthe optimum BG quantity is set every hue, are created, and the tables,in which influence of graininess caused by the black ink can be possiblyreduced while maximizing the color reproduction region in the printer,can be set.

[0076] In the conventional system, since non-linear characteristic incase of the mixture of plural color inks can not be sufficientlyabsorbed, there occurred a problem that distorted characteristic isappeared in lightness, hue and chroma. However, according to the presentembodiment, the internal ink quantity can be smoothly changed by amethod of dividing a cube into plural tetrahedrons, separating thosetetrahedrons into plural triangles and connecting points of the samelevel value of the ink quantity on the three sides of each triangle,thereby realizing color reproduction of suppressing the distortedcharacteristic in the lightness, the hue and the chroma.

[0077] In the K ink dyeing UI 1402-1 shown in FIG. 14, since the K inkdyeing points on each line set in the step S3-4 shown in FIG. 3 can bemanually instructed, a sensitive adjustment can be performed.

[0078] (Second Embodiment)

[0079] The second embodiment which is obtained by modifying the firstembodiment executes non-linear approximation processing of ink quantitycontour lines as in FIG. 16 in a step S7-5 shown in FIG. 15.

[0080] According to the second embodiment, a contour line varyingrectangularly can be corrected into the contour line which is smoothlyand sequentially varied. Accordingly, generation of a pseudo outline incase of extreme changing of the ink quantity can be suppressed.

[0081] In the following explanation, the same processing as that in thefirst embodiment will be omitted to explain, and processing differentfrom that in the first embodiment will be explained.

[0082] In case of executing two-dimensional interpolation processing toa target triangle in the step S5-3 shown in FIG. 5, the non-linearapproximation processing of the above ink quantity contour lines isexecuted.

[0083] The two-dimensional interpolation processing for the targettriangle executed in the second embodiment will be explained withreference to FIG. 15.

[0084] The step S7-1 is a step of detecting maximum value points of theink quantity on three sides of the target triangle. The step S7-2 is astep of obtaining magnitude relationship among three maximum values ofthe three sides. The step S7-3, which is an interpolation step among themaximum value points on the three sides, performs an interpolationoperation from values of both ends among the points by connecting thepoints of the three maximum values on the three sides by straight lines.The step S7-4 is a step of creating an ink contour line by connectingink quantity same-level points on total six lines consisted of the threesides of the target triangle and three straight lines created accordingto the three maximum value points. A step S15-5, which is a step ofexecuting the non-linear approximation processing of the ink quantitycontour lines, non-linearly approximates a portion of rectangularlychanging in a region inside the triangle among the ink quantity contourlines created in the step S7-4 such that the ink quantity contour linesare smoothly created.

[0085] It should be noted that processing executed in the steps S7-1 toS7-4 are the same as those in the first embodiment.

[0086] A detailed explanation of the step S15-5 will be given withreference to FIG. 17.

[0087] A step S17-1, which is a step of setting an approximationparameter a, sets the non-linearity degree in case of creatingnon-linear approximation curves. The approximation parameter a can beset as a =1, 2, 3, 4, . As in FIG. 18, when the parameter a is set asa=1, the approximation degree increases with linear approximation, andwhen the parameter a is increased as a =2, 3, 4, the approximationdegree decreases while smoothness of the ink quantity contour linesincreases. A user can set the approximation parameter a in accordancewith characteristic of a printer. Although there are various methods asmethod of creating the non-linear approximation curves, e.g., in case ofusing spline curves, creation of the non-linear approximation curves canbe attained by setting that when the parameter a=1, a curve is a primaryspline curve, when the parameter a=2, a curve is a secondary splinecurve, when the parameter a=3, a curve is a tertiary spline curve, andwhen the parameter a=4, a curve is a quartic spline curve.

[0088] A step S17-2, which is a step of setting an initial value i=d−s,sets the initial value of the ink quantity contour line in case ofexecuting the non-linear approximation processing. A step S17-3 is astep of judging whether or not relationship among d, i and j isexpressed by an expression of d>i>j. If No in the step S17-3, the flowreturns to a portion 5-2 to terminate the non-linear approximationprocessing of the ink quantity contour lines. If Yes in the step S17-3,the flow advances to a step S17-4.

[0089] The step S17-4, which is a step of setting vertexes, setsvertexes G0, G1, G2 and G3 structuring a contour line when the initialvalue i is set as i=75 in an example in FIG. 16. A step S17-5, which isa step of creating the non-linear approximation curves, createsnon-linear curves on the basis of a set value of the approximationparameter a and set vertexes. In an example in FIG. 16, for the vertexesG0, G1, G2 and G3 respectively connected by a thin line, theapproximation curve represented by a thick line is created. A step S17-6is a step of performing an operation of i=i−s. In the example in FIG.16, the value of i is set as i=60, thereafter, a loop processing fromthe step S17-3 to the step S17-6 is repeated.

[0090] When the value of i is set as i=60, vertexes H, H1 and H2 areselected in the step S17-4 and the non-linear approximation curve iscreated in the step S17-5. When the value of i is set as i=45, vertexesI2, I3, I4 and I5 are selected in the step S17-4 and the non-linearapproximation curve is created in the step S17-5.

[0091] When the value of i is set as i=30, a judgment result of No isselected in the step S17-3, and the flow returns to a portion 5-2.

[0092] Hereinafter, with respect to a case that the ink quantity curveson the three sides are different from those in the example in FIG. 16,operations regarding examples in FIGS. 9, 10 and 19 will be explained.FIG. 9 shows an example of a case that the ink quantity maximum valueson the three sides are identical each other. In this case, the contourlines as shown in FIG. 11 are created similar to a case of the firstembodiment. FIG. 10 shows a case that the ink quantity on one side isequal to zero and the maximum values on other two sides are identicaleach other. Also, in this case, the contour lines as shown in FIG. 10are created similar to a case of the first embodiment. FIG. 13 shows acase that the maximum values on the two sides are identical each otherand points of these maximum values exist on a point A. In this case, thenon-linear approximation processing of the ink contour lines as in thestep S15-5 is executed, and contour lines as shown in FIG. 19 arecreated.

[0093] The ink contour lines every ink color are shown in FIGS. 20A to20D.

[0094]FIG. 20A indicates the contour lines of the C ink quantity, andthis case corresponds to a case in FIG. 19. FIG. 20B indicates thecontour lines of the M ink quantity, and this case corresponds to thecase in FIG. 10. FIG. 20C indicates the contour lines of the Y inkquantity, and this case also corresponds to the case in FIG. 10. FIG.20D indicates the contour lines of the K ink quantity. This casecorresponds to the case in FIG. 10, however, since the K ink is injectedfrom halfway, a region of which ink quantity is zero widely exists andthe contour lines of the K ink quantity are created from halfway.

[0095] (Third Embodiment)

[0096] In the above embodiments, as ink colors available in a printer, acase of using four colors of C, M, Y and K is indicated. However, a caseof such a printer available for total six colors of additionally usinglight and dark inks for cyan and magenta can be also easily realized byonly adding two ink colors. In this case, similar to a case of settingthe ink (K ink) dyeing point, a new UI of setting a dark ink dyeingstart point is provided for the case in FIG. 21, and dark cyan and darkmagenta inks dyeing points can be controlled in a manner that dark inkdyeing points can be three dimensionally and sequentially controlled bytotal seven points on lines W-Bk, W-C, W-M, W-Y, W-R, W-G and B-Bk.

[0097] In case of dealing another color ink such as red, green or thelike other than the C, M, Y and K colors, intermediate points RM, RY,GY, and GC are newly set on intermediate portions between points R andM, R and Y, G and Y, and G and C. Then, total ten tetrahedrons ofW-C-B-Bk, W-B-M-Bk, W-M-RM-Bk, W-RM-R-Bk, W-R-RY-Bk, W-RY-Y-Bk,W-Y-GY-Bk, W-GY-G-Bk, W-G-GC-Bk and W-GC-C-Bk are defined, therebyeasily providing the optimum ink color separation in the printeravailable for six colors even in case of increasing ink colors.

[0098] In this manner, in case of using light color ink other thancolors of the C, M, Y and K inks, the optimum color separation can beprovided.

[0099] Similarly, in case of using another color ink such as red, greenor the like, the optimum color separation can be provided.

[0100] (Fourth Embodiment)

[0101] The above embodiments are performed by a controller inside theprinter. However, the present invention is not limited to this case, butthe present invention can be realized also in case of downloadingrelated data to a LUT in software of a driver inside a computer shown inFIG. 14.

[0102] (Fifth Embodiment)

[0103] In the above embodiments, as a device for outputting image datato the printer, the computer as shown in FIG. 14 is used. However, thedevice is not limited to the computer, but the device, which cantransmit image data to the printer such as the one capable oftemporarily storing image data taken by a digital camera or the like andtransmitting the image data to the connected printer, is applicable.

[0104] In the above mentioned embodiments, the device for transmittingthe image data and the printer exist independently. However, the presentinvention can be conducted by only the printer itself, in a case wherethe image data which is input by input means such as the digital cameraor the like is stored into any memory medium, and an equipment ofcapturing the image data in that memory medium is attached to theprinter itself.

[0105] (Sixth Embodiment)

[0106] In the above embodiments, as shown in FIG. 14, as an input devicefor inputting patch samples, a colorimeter is used. However, the inputdevice is not limited to the colorimeter but may be any device such as aflat-bed scanner, a drum scanner or the like which can capture printdata into the computer and check characteristic of inks used in theprinter.

[0107] (Seventh Embodiment)

[0108] In the above embodiments, as an input color space of an ink colorseparation table for defining a color reproduction region of a colorprinter, an RGB color space is used. However, the input color space isnot limited to the RGB color space but may be any one capable of threedimensionally defining the color reproduction region of the printeraccording to C, M and Y data or three parameters of a, c and b.

[0109] (Other Embodiments)

[0110] The present invention includes a case where program codes ofsoftware for realizing functions of the above embodiments are suppliedto an apparatus connected to various devices or a computer in a systemso as to realize the functions of the above embodiments and operate thevarious devices and then the various devices are to be operated inaccordance with programs stored in the computer (or CPU or MPU) in thesystem or the apparatus.

[0111] In this case, the program codes themselves of the softwarerealize the functions of the embodiments, and the program codesthemselves and means for supplying the program codes to the computer,e.g., a storage medium storing such the program codes constitute thepresent invention.

[0112] The storage medium for storing the program codes can be, e.g., afloppy disk, a hard disk, an optical disk, a magneto-optical disk, aCD-ROM, a magnetic tape, a non-volatile memory card, a ROM or the like.

[0113] It is needless to say that the program codes are included in theembodiments of the present invention not only a case where the functionsof the above embodiments are realized by the execution of the suppliedprogram codes by the computer, but also a case where the program codesrealize the functions of the above embodiments cooperating with an OS(operating system) functioning on the computer or another applicationsoftware.

[0114] Further, it is needless to say that the present inventionincludes a case where the supplied program codes are once stored in amemory provided in a function expansion board inserted in the computeror a function expansion unit connected to the computer, and then a CPUor the like provided in the function expansion board or the functionexpansion unit executes all the process or a part thereof on the basisof the instructions of the program codes, thereby realizing thefunctions of the above embodiment.

[0115] As above, the present invention has been explained on the basisof the preferable embodiments. However, the present invention is notlimited to the above embodiments, but may be modified in various mannerswithin the scope of the following claims.

What is claimed is:
 1. An image processing method, which creates a tablefor separating color into color of coloring agent available in an imageformation apparatus, characterized in that: a maximum line in a colorreproduction region of the image formation apparatus is defined;internal lines in the color reproduction region of the image formationapparatus are defined; and interpolation processing is executed on thebasis of the maximum line and the internal lines, thereby creating thetable.
 2. An image processing method, which creates a table forseparating color into color of coloring agent available in an imageformation apparatus, characterized in that: a first line from black towhite is defined; plural second lines from white to primary color andsecondary color are defined, plural third lines from the primary colorand the secondary color to black are defined; and the table is createdaccording to the first line, the second lines and the third lines.
 3. Amethod according to claim 2, wherein it is possible to control inkdyeing points on the first line and the third lines.
 4. A methodaccording to claim 3, wherein the control of the ink dyeing points isperformed on the basis of a manual instruction by a user.
 5. A methodaccording to claim 2, wherein a start of dyeing dark coloring agent onthe first line, the second lines and the third lines is controlled in animage processing method which creates a table of an image formationapparatus for performing an image formation using plural coloring agentshaving different density for the same color.
 6. A method according toclaim 2, wherein a coloring agent quantity contour line is calculated onthe basis of the coloring agent quantity on each side of a plane definedby the plural coloring agents.
 7. A method according to claim 6, whereinnon-linear curve approximation processing is used in case of forming thecoloring agent quantity contour line.
 8. A method according to claim 2,wherein a cube indicating a color space is divided into pluraltetrahedrons, and interpolation processing is executed by connectingpoints having the same coloring agent quantity on three sides of eachtriangle indicating side planes of the divided tetrahedrons.
 9. An imageprocessing apparatus, which creates a table for separating color intocolor of coloring agent available in an image formation apparatus,comprising: means for defining a first line which is from white toblack; means for defining plural second lines which are from white toprimary color and secondary color; means for defining plural third lineswhich are from the primary color and the secondary color to black; andmeans for creating the table according to the first line, the secondlines and the third lines.
 10. A program for realizing an imageprocessing method which creates a table for separating color into colorof coloring agent available in an image formation apparatuscharacterized in that a first line from black to white is defined;plural second lines from white to primary color and secondary color aredefined; plural third lines from the primary color and the secondarycolor to black are defined; and the table is created according to thefirst line, the second lines and the third lines.